The present invention pertains to devices for producing vibratory motion and, more particularly, to devices for producing linear vibratory motion.
Vibrating devices are widely used in industry for actuating oscillating conveyors, shaking screens, feeders, inspection tables, container fillers, bin and hopper agitators, packing devices to increase the compaction and density of materials and to aid the compacting effect of rollers in earthmoving and earthfill operations. The use of vibrating devices has increased extensively in the food handling and processing fields, for products such as corn, beans, peas, etc., where oscillating devices provide advantages such as gentle handling, control-liability, reliability and improved sanitation.
Several types of vibrating devices are now employed, including electro-magnetic, pneumatic, rotating eccentric weights and cam operated eccentric drive arms. The electro-magnetic and pneumatic linear motion vibrators are inherently high frequency and short stroke units and are thus limited to use with relatively low loads. Units with rotating eccentric weights provide only orbital reaction to the driven unit and not linear motion. In those units having eccentric drive arms, the arms are connected to stationary mountings thus transmitting much of the reaction force to the floor or building structure and requiring counterbalancing or isolation devices.
A widely used type of vibratory motion generating device which avoids the difficulties of the vibrators discussed above is the contra-rotating type which employs a pair of eccentric weights geared to rotate in opposite directions about a common axis. Loveless U.S. Pat. No. 3,173,300 illustrates a device of this type. Contra-rotating vibrators of the prior art, such as the Loveless device, require separate drive means thus complicating the mounting of the device as well as increasing the cost thereof. An additional disadvantage of the prior art devices is the lack of any means for readily varying the direction of the vibratory motion.
Among the primary objects of the present invention is the provision of a vibratory motion generating device of the contra-rotating type which incorporates the drive means and contra-rotating weights into a unified, compact structure. It is also an object of the invention to provide a self-contained contra-rotating vibrator which includes a sealed housing enabling the device to withstand the cleaning and sanitizing procedures employed in food handling installations.
A further object of the invention is the provision of a contra-rotating vibrator producing linear vibrations and which may be readily adjusted to vary both the direction of the vibratory motion and the frequency thereof.